Combustion apparatus



April 2, 1946. R. H. GODDARD GOMBUSTI IION APPARATUS Filed March 9, 19422 Sheet s-Sheet l I c/ wr- Faierf'ZG j April 2, 1946. R. H. GODDARD2,397,553

COMBUSTION APPARATUS Filed March 9, 1942 2 Sheets-Sheet 2 Patented Apr.2, 1946 FFlCE COMBUSTION APPARATUS Robert H. Goddard, Boswell, N. Mean,asslgnor of one-half to The Daniel and Florence Guggenheim Foundation,New York, N. Y., a corporation of New York Application March 9, 1942,Serial No. 433,963

(Cl. (so-35.6) I

13 Claims.

This invention relates to a. combustion chamber in which mixed oxidizingand combustible gases or vapors may be continuously burned. Whilecapable of general application, my improved combustion chamber isparticularly designed and adapted for use in the propulsion of rocketsor rocket craft.

It is an important object of my invention to provide improved andemcient cooling for a combustion chamber of light construction which isexposed to extremely high combustion temperatures.

A further object of my invention is to provide improved regulation ofthe fuel feed in a combustion chamber. In the preferred form, I maintainthe fuel feed in a definite relation to the axial displacement of thecombustion chamber in its supporting structure, which displacement isrelated to changes in axial thrust produced by the combustion gases insaid chamber.

I also provide improved means for reducing the surfac tension of theliquid fuel spray by the application of heat to the liquid fuel, and Iprovide means for supporting the combustion chamber so that the chamberwill be at all times under axial tension rather than compression.

My invention further relates to arrangements and combinations of partswhich will be hereinafter described and more particularly pointed out inthe appended claims.

Preferred form of the invention are shown in the drawings, in which Fig.l is a sectional front elevation of my improved combustion chamber;

. Fig. 9 is a detail sectional view showing additional modifiedstructure.

Referring to Fig. 1, I have shown a combustion chamber comprising aninner casing 20, an intermediate casing or Jacket 2|, and an outercasing 22, said parts being held in spaced relation by tie rods orbraces 23 (Fig. 4) secured to each of the casing members 20, 2| and 22.

The inner casing 20 comprises a, cylindricial middle portion 25, aconical entrance portion 2', a conical discharge portion 21, and adischarge nozzle 28. A liquid oxygen supply pipe is connected into thespace 3| between the outer casing 22 and the intermediate casing orjacket 2| and adjacent the outer end of the nozzle 28. The space 3| isgradually reduced in cross sectional area upward as viewed in Fig. 1 andis closed at its upper end. This gradual reduction in cross sectionalarea facilitates the maintenance of uniform flow. The liquid oxygen isfurnished from any suitable supply under pressure, and the flow ofliquid oxygen is controlled by a valve 32.

The intermediate casing or jacket 2| is provided with a multiplicity ofperforations 33( Fig.

4) through which narrow streams or Jets J of liquid oxygen are proiectedagainst the outer surface of the inner casing 20 to cool said innercasing and to prevent melting or burning thereof by the extremely hotcombustion gases developed within the chamber.

Such narrow streams are superior to sprays for the reason that there isconsiderable friction tending to retard the motion of small drops,

Fig. 2 is an enlarged sectional front elevation 85 particularly in a gasof high pressure and denof certain gasoline feed devices for saidchamber;

Fig. 3 is a sectional plan view, taken along the irregular line 33 inFig. 2;

Fig. 4 is an enlarged detail sectional front elevation of an upperportion of the combustion chamber;

Fig. 4 is a slightly modified detail sectional plan view, taken alongthe line 4'-4' in Fig. 4;

Fig. 4 is a fragmentary side elevation, looking in the direction of thearrow 4" in Fig. 4*;

Fig. 5 is a detail sectional plan view of certain nozzle structure,taken along the line 55 in Fi 1:

Fig. 6 is a fragmentary sectional front elevation showing a bracedconstruction;

Fig. 7 is a front elevation of a, brace. or bracket;

Fig. 8 is a partial sectional front elevation of a modified form ofcombustion chamber; and

sity, which would reduce the speed. and hence the cooling effect, ofsprays.

In order to prevent rebound and scattering of the liquid as it engagesthe casing 20, I provide recessed portions or dents 25 in the casing 20,which recessed portions are convex inward and concave outward withrespect to the casing 20. The recessed portions 35 are aligned with thejets J and as each jet strikes one of these recessed portions insubstantial alignment therewith, the jet spreads out sldewise butdevelops enough centrifugal force to maintain the liquid in closeengagement with the casing surface, so

' that the inner casing is thus effectually cooled.

Such engagement, besides cooling'the casing wall 20, also evaporates thecold liquid oxygen. The oxygen vapor or gas thus produced passes upwardalong the annular space 36 between the walls 20 and 2| and enters thecombustion chamber as a conical sheet through an annular slot or opening36 (Fig. 4) at the top of the cylindrical portion 26 and just below theconical entrance portion 26. It will be noted that the annular space 36increases in cross section upwardly, to provide increased space for theevaporated and expanding oxygen gas. The conical sheet of oxygen gas andthe conical spray of gasoline vapor from a spray orifice to be describedimpinge from reverse directions, which causes very intimate mixture. Thegreater weight and volume of oxygen carries the gases well up in theentrance portion 26, where mixing mainly takes place and where activecombustion is initiated.

In the preferred form, the recessed portions I or dents 35 are moreclosely grouped and of smaller area in those portions of the combustionchamber where the highest temperatures are encountered. These smallerand more closely grouped recessedportions are indicated at 35' in Fig.'1. The cooling effect in this portion of the cylinder is increased inpart by the increased number and closer spacing of the jets, and also bythe sharper curvature of the recessed surfaces, which increases thecentrifugal action.

In the lower conical portion 21. of the combustion chamber and in thedischarge nozzle 28, the separate recessed portions or dents cannot beused, as they would break up the streamlined surfaces which areessential to prevent interference with the high velocity movement of thecombustion gases as they approach the nozzle 28 While it is necessary tocool the inner casingto prevent destruction thereof, it is alsodesirable to prevent cooling of the gases in the combustion chamber asfar as possible, and for this reason I provide a thin refractory lining44 within the parts and 21 of the combustion chamber and within thedischarge nozzle 28.

Thisglining is preferably formed in relatively small sections or shellsand is of such thickness in relation to the thicknes of the casing 20that the inner surface of the casing 26 is heated just below itssoftening point and that the inner surface of the lining 44 is similarlyheated just below its softening point. In this way, the casing 20 isprotected, while at the same time the combustion gases are maintained atthe highest permissible temperature.

Small shells 44 of refractory material are preferable because of thetendency of unequal expansion to produce cracks over large areas. In theform shown in Figs. 4* and 4 the recessed portions or dents 35 are quiteclose together and the shells of refractory material over the dents willbe held in place by the arched or concave shape of the chamber wall.

A gasoline feed chamber 50 (Fig. 2) is provided at the entrance end ofthe combustion chamber, to which gasoline may be supplied through aflexible feed pipe 5|. The chamber 50 contains a sleeve 52 fixed thereinand having valve openings asa'mes -member 59 to the plate 58.

If the valve openings 53 and 55 are aligned, in whole or in part,gasoline from the outer annular space 60 in the gasoline chamber 50 willpass through the valve openings 53 and 55 and thence downward throughthe inner casing 54 to a nozzle opening 62, provided with any usualdevice 63 for imparting a whirling motion to the gasoline as it is fedthrough the nozzle opening 62 to the upper portion 26 of the combustionchamber, which portion has a refractory lining 64. Means for producingrelative axial motion between the sleeves 52 and 54 will be hereinafterdescribed.

The injected gasoline preferably forms a hollow cone of spray, justinside the refractory lining 64, this spray meeting the oxygen gasstream from the slot 38 at a substantial obtuse angle. The slot 38 isback of the refractory lining 64 and out of line with the gasolinespray, so that gasoline cannot enter the oxygen jacket 2| accidentally,in the absence of a high speed stream of oxygen gas, and thus produce anexplosive mixture when the oxygen starts to flow.

It will be noted'by reference to Fig. 1 that the gasoline enters thecombustion chamber as a spray from the single nozzle opening 62, whereasthe oxygen enters the chamber almost entirely in gaseous condition andthrough the extended circumferential entrance slot 38. In order toimprove the mixture and to vaporize the gasoline as much as possible, Iprovide special means for heating the gasoline as it enters the portion26 of the combustion chamber, such special means being necessary inorder to break up the gasoline into very fine drops in the relativelyshort available distance of travel.

For this purpose, I provide an annular passage 65 (Fig. 2) surroundingthe discharge end of the gasoline chamber 50 and connected by a by-passpipe 66 to the upper end of the annular oxygen space 36. A shut-oilvalve 61 controls the flow and its surface tension substantially reducedbefore it engages the main gaseous oxygen supply, which enters throughthe annular slot 38.

For most eflicient operation, it is necessary that the proportions ofoxygen and gasoline be correctly maintained, and as variations in theamount of oxygen supplied unavoidably occur, due to changes in the ratedevaporation of the oxygen and toother variable causes, provision is madeto vary the gasoline feed with reference to variations in flow of oxygengas or vapor to the combustion chamber.

To accomplish this regulation, advantage is taken of the reactive effectof the combustion gases issuing from the nozzle 28 against the closed orupper end of the combustion'chamber II. The more complete and perfectthe eombustio the stronger will be these reactive forces.

In order to utilize these forces in the regulation of the gasoline feed,I mount the combustion chamber on an annular plate or ring I! (Fig. 1)and I provide a plurality of supporting rods 18, each of which issecured to the ring II at its lower end. At its upper end, each ofthesupporting rods I3 is connected to a chambered piston ll, slidable in afixed sleeve and pressed downward by a relatively strong coil spring 15.Guide blocks ll on the supporting rods 18 loosely engage the outercasing 22 of the combustion chamber and center the casing but'withoutexerting pressure thereon.

With the chamber thus supported, the casings 28, II and 2! are undertension, rather than compression. The reason for supporting the chamberand casings under tension rather than under compression is because allof these thin structures will withstand tension but not compression,except when they are sustaining high internal gas pressure. Moreover,the thin refractory shells 44* cannot withstand the bending which wouldaccompany compression. Tension, on the other hand, merely opens slightlythe spaces between the shells.

With this construction, any increase in the reactive forces from thenozzle 28 will cause the chamber 28 to move upward against the pressureof the springs 18, carrying with it the gasoline chamber 58 and theouter valve sleeve 52. As the inner valve sleeve 54 normally remainsfixed, the openings 53 and 55 will be more nearly aligned and the flowof gasoline will correspondingly increase. The flexible bellows member59 permits such relative upward movement of the gasoline chamber 58.

As the thrust increases, more gasoline will be admitted through theopening 55, and this will continue until the rate of gasoline flow issuch as to produce the greatest thrust for the oxygen flow that istaking place. This oxygen flow, although mainly dependent on the amountof open- ,ing of the valve 32 (Fig. 1), also depends largely on thetemperature of the chamber and jacket walls. Further upward movement ofthe chamber 28 and gasoline chamber 58 will not increase the thrust,since the excess of gasoline over that required for best combustion willretard the oxygen flow by creating extra chamber pressure. Thisretardation of the oxygen flow will reduce the combustion, and thevelocity of the gases from the nozzle will fall.

In order to prevent undesirable oscillations or hunting of thecombustion chamber and particularly those produced by the coaction ofthe nozzle thrust acting on the valve 58 and the springs I6, I provideperforated pistons 88 in cylindrical openings 8| in the pistons 14.These perforated pistons 88 are mounted atthe lower ends of rods 83fixed in the frame F, so that a. dash-pot effect is produced andoscillations of the combustion chamber are prevented. 'I'o permit upwardmovement of the oxygen feed pipe 38, a telescoping joint 84 (Fig. 1) isprovided.

It is desirable that the nozzle opening 62 at the bottom of the gasolinechamber 58 be positively closed when the apparatus is not in use. Forthis purpose, I mount the plate 58 (Fig. 1) at the lower end of a sleeveor plunger 88 slidable vertically in a bearing in the frame F and havinga pin and slot connection with a forked bell crank 81 and pull rod 88.

Whencombustion is to be discontinued, the rod 88 is pulled, depressingthe sleeve 88 and forcing a valve member 88 at the lower end of the rod51 against the lower end of the combustion chamber 58, thereby closingthenozzle opening 82. The parts may be frictionally held in thisposition. when active operation of the apparatus is to be resumed, theparts are manually restored to the position shown in Fig. 1, whichposition will be maintained during operation by friction and by thegaseous pressures developed in the apparatus.

Precooling of the apparatus is desirable to prevent gas bind in quickstarting. To accomplish this result, the oxygen valve 32 may be openedslightly, some time before the gasoline valve 88 is opened. A slowevaporation of oxygen will then precool the casings 28, 2i and 22. Thismethod of precooling is safe, since the gasoline valve member 83 istightly closed and hence leakage of gasoline vapor into the chamber,which might form an explosive mixture, is avoided.

As the parts adjacent the annular oxygen feed slot 88 are relativelyunsupported, -I provide brackets or braces 98 (Figs. 6 and '7) which arevertically disposed so that they do not interfere with the flow ofoxygen gas but which nevertheles firmly support the upper edge of theinner casing 28.

In Fig. 9 I have shown a variation of the nozzle structure shown in Fig.5, with the nozzle formed of a conical metal sleeve 85 having a smoothinner surface 96 and outer recessed portions or dents 81, similar to 35of Fig. 4 or 35* in Fig. 4 .These dents 81 are more effective than theconcave axial ribbed portions 48 of Fig. 5', since centrifugal forcecauses intimate contact of the spray with the metal surface in alldirections around the Jets J and gives a smooth, streamlined, innersurface, but have less efficient total cooling effect, due to theincreased thickness of metal between the recessed portions 81.

In Fig. 8 I have shown a modified construction of combustion chamber I88in which the chamber is substantially spherical, rather than of theshape shown in Fig. 1. This construction has certain advantages forcombustion chambers of small size but is less desirable for the largerunits, as its capacity can only be increased by an increase in diameter,whereas increased capacity can be obtained in the preferred formby aniiicrease in the axial length of the cylinder. The thin refractorylining of the nozzle consists pref era-bly of sections l8l (Fig. 8) ofshort axial length, so as not to be subject to severe expansion forces.They are beveled at I82 on the edges where the gas stream impinges, soas not to interfere with gas flow.

It will thus appear that I have provided simple and effective apparatusfor cooling and continuously operating a combustion chamber and forautomatically regulating the supply of fuel thereto.

The provision made for movably mounting the combustion chamberin thefixed frame and for varying the gasoline feed in accordance with theaxial position of the combustion chamber is not claimed herein but formsthe subject matter of a divisional application Serial No. 647,607, filedFebruary 14, 1946.

Having thus described my invention and the advantages thereof, I do notwish to be limited to the details herein disclosed, otherwise than asset forth in the claims, but what I 'claimis:

. tions formed therein and providing concave depressions in the outersurface of said combustion chamber, and means to direct a jet of coldliquid against each of said concave depressed portions at the outside ofsaid combustion chamber.

2. In combustion apparatus, a combustion chamber having a thin metalside wall with a plurality of spaced and inwardly displaced portionsformed therein and providing concave depressions in the outer surface ofsaid combustion chamber, means to direct a jet of cold liquid againsteach of said concave depressed portions at the outside of saidcombustion chamber, and means to conduct the vapors of said cold liquidproduced by such engagement to the entrance end of said combustionchamber.

3. In a combustion apparatus, wiiombustion chamber comprising an innercasing, a perforated intermediate casing and 'an outer casing, saidinner casing having an entrance portion for combustion liquids at oneend and a nozzle outlet for combustion gases at the other end, means tomaintain said three casings in spaced relation, means to supply a coldliquid under pressure to the space between the outer and intermediatecasings, said liquid being projected by said pressure in spaced jetsthrough said perforated intermediate casing and against said innercasing,

and means to conduct the vapors of said cold liquid produced by suchengagement toward'the entrance end of said combustion chamber, and thedistance between the inner and intermediate casings increasingprogressively in the direction of flow of said vapors from the nozzleend to the entrance end of said combustion chamber and therebyrelatively reducing the rate of flow of said vapors through the annularspace between the inner and intermediate casings.

4. In a combustion chamber, an inner casing,

a perforated intermediate casing and an outer casing, means to maintainsaid three casings in spaced relation, and means to supply anoxidizasamss that portion of the combustion chamber which is subject tothe greatest heat, and said depressed portions being moresharply'concave where they are more closely disposed.

7. In combustion apparatus, a combustion chamber having a thin metalside wall with a plurality of spaced and inwardly displaced portionsformed therein and providing concave depressions in the outer surface ofsaid combustion chamber, and means to direct a'jet of cold liquidagainst each of said concave depressed portions at the outside of saidcombustion chamber, and the radii of curvature of said depressedportions varying inversely to the temperature ratios in said combustionchamber when said chamber is in continuous operation.

8. In a combustion apparatus, a combustion chamber having a dischargenozzle with its side walls comprising longitudinally extending andclosely adjacent casing portions which are inwardly convex and outwardlyconcave, and means to direct jets of a cold oxidizing liquid against theouter and intermediate casings, said liquid being projected by saidpressure in spaced jets through said perforated intermediate casing andagainst said inner casing, and said inner casing having spaceddepressions aligned with said jets and presenting concave surfacesthereto whereby said liquid maintains close cooling engagement with saidinner casing.

5. In combustion apparatus, a combustion chamber having a thin metalside wall with a plurality of; spaced and inwardly displaced portionsformed therein and providing concave depressions .in the outer surfaceof said combustion chamber, and means to direct a jet of cold liquidagainst each of said concave depressed portions at the -outside of saidcombustion chamber, said depressed portions being more closely disposedin that portion of the combustion chamber which is subject to thegreatest heat.

6. In combustion apparatus, a combustion chamber having a thin metalside wall with a plurality of spaced and inwardly displaced portionsformed therein and providing concave depressions in the outer surface ofsaid combustion chamber, and means to direct a jet of cold liquidagainst each of said concave depressed portions at the outside of saidcombustion chamber, said depressed portions being more closely disposedin the outer concave surfaces of said longitudinally extending portions.

9. In a combustion apparatus, a combustion chamber having asubstantially conical entrance portion, means to introduce a spray ofliquid fuel through the outer end of said conical portion, and means tointroduce anbxidizing liquid as a conical sheet through an annular slotadjacent the inner'end of said conical entrance portion, said oxidizingliquid and said liquid fuel impinging as they approach from relativelyreverse directions.

10. In a combustion chamber, an inner casing, a perforated intermediatecasing and an outer casing, means to maintain said three casings inspaced relation, means to supply an oxidizing liquid under pressure tothe space between the outer and intermediate casings, said liquid beingprojected by said pressure in spaced jets through said perforatedintermediate casing and against said inner casing, said inner casinghaving spaced depressions aligned with said jets and presenting concavesurfaces thereto, and the inner faces of said inner casing and of saiddepressed portions thereof being covered with inner refractory shells.

11. In a combustion chamber, an inner casing, a perforated intermediatecasing and an outer casing, means to maintain said three casings inspaced relation, means to supply an oxidizing liquid under pressure tothe space between the outer and intermediate casings, said liquid beingprojected by said pressure in spaced jets through said perforatedintermediate casing and against said inner casing, said inner casinghaving spaced depressions aligned with said jets and presenting concavesurfaces thereto, and the inner faces of said inner casing and of saiddepressed portions thereof being covered with an inner refractorysurface comprising sectional plates of relatively small area and ofrelatively slight thickness.

.12. In combustion apparatus, a combustion chamber, separate means tointroduce an oxidizing liquid and liquid fuel therein, means to vaporizethe oxidizing liquid before it enters the combustion chamber, and meansto by-pass a small portion of said oxidizing vapor to the point ofentrance of said. liquid fuel to said chamber, whereby initialcombustion thereof preheats the fuel spray and reduces the surfacetension thereof.

13. In a combustion apparatus, a combustion chamber having asubstantially conical entrance portion, means to'intr'oduce a spray ofliquid fuel through the outer end of said conical portion, 1nd

means to introduce an oxidizing liquid as a conical sheet through anannular slot adjacent the inner end of said conical entrance portion,said oxidizin 'liqu'id and said liquid fuel impinging as they approachfrom relatively reverse directions, and

ROBERT H. GODDARD.

